Air pollution is one of the major environmental challenges facing the world today. According to the 2014 WHO report, air pollution in 2012 caused the deaths of around 7 million people worldwide, an estimate roughly matched by the International Energy Agency.
The introduction of contaminants into the natural environment may cause adverse changes to human life. For instance, smog hanging over cities is the most familiar and obvious form of visible air pollution. The impact of pollution is even more severe in developing countries than developed countries, where the competitiveness of these countries is economically depended on extraction of natural resources and heavy industries.
Air pollution is a significant risk factor for a number of pollution-related diseases and health conditions affecting millions of people annually. Over the past 30 years, researchers have identified a wide array of health effects including respiratory diseases such as asthma and changes in lung function, lung cancers, COPD, heart diseases, cardiovascular diseases, adverse pregnancy outcomes such as preterm birth, stroke and etc. These are believed to be associated with air pollution exposure.